Dilatant behavior of a solution of a sulfonated polymer

ABSTRACT

A method for improving the antimisting properties of an organic liquid which comprises the step of dissolving about 0.1 to about 3.0 weight percent of a neutralized sulfonated polymer in such organic liquid, having a solubility parameter of less than 9, wherein said neutralized sulfonated polymer has about 5 to about 200 meq. of pendant sulfonate groups per 100 grams of polymer and about 90.0 to 100% of said sulfonate groups are neutralized, wherein the solution of the organic liquid and the neutralized sulfonated polymer has an approximate polymer concentration, C A , which can be characterized by the formula: ##EQU1## wherein [η] is the intrinsic viscosity of said solution and the polymer concentration range is 0.1 times to 10 times C A .

FIELD OF THE INVENTION

A process for improving the antimisting properties of a jet aviationfuel.

BACKGROUND OF THE INVENTION

Most polymer solutions exhibit shear thinning (or pseudo-plastic)behavior while simpler, low molecular weight fluids, such ashydrocarbons and water exhibit Newtonian behavior. It was found thatsolutions of associating polymers can, on the other hand, exhibit shearthickening (or dilatant) behavior regardless of their molecular weightif they are prepared in given concentration ranges. These concentrationranges can be shifted by adding cosolvents that are capable of changingthe associating strength or nature according to a criteria that isdisclosed below. By properly choosing the cosolvent and adjusting itsconcentration, the viscosity range of the fluid, as well as its viscousbehavior with time under shear, can be altered.

Polymeric materials are useful as viscosity enhancers when dissolved inthe appropriate solvent system. The principle reason for this behavioris due primarily to the large volume which a single macromolecular chaincan occupy within the solvent. An increase in the size of the chainproduces a concomitant enhancement in the solution viscosity. However,when the polymer chain is placed in a shear field, segmental orientationtakes place in direction of the shearing force. The viscosity of thefluid dramatically drops due to this orientation phenomena. This is atypical behavior of most solutions containing dissolved polymericmaterials. However, if the polymer molecule has a high molecular weightwith a relatively flexible backbone and the solvent viscosity issufficiently high, different behavior is anticipated.

It has been shown by several groups that, with increasing shear rates,the viscosity should show a decrease, followed by a minimum value and asubsequent mild increase in cases where both solvent viscosity andpolymer molecular weight are very high. This latter effect gives rise toa mild dilatant behavior. However, the above-mentioned conditionsrequired for the appearance of shear thickening behavior in thesepolymeric solution systems are not applicable for many technologicallyinteresting fluids. In most of the common synthetic polymers, it isdifficult, from a synthetic viewpoint, to obtain sufficiently highmolecular weight and, in addition, most solvents (for example, water)have rather low viscosities.

This invention discloses the novel and unexpected result that solutionsof sulfonated polymers, which are soluble in a system of an organicliquid are capable of enhancing the viscosity of these solutions underrelatively broad shear conditions. With these unique polymericmaterials, dilatant behavior occurs in fluids which are of extremetechnological utility. It is further observed that under the identicalexperimental conditions, the viscosity of the individual copolymercomponents show the normal shear thinning behavior.

The modification of fluids with polymeric additives is of extremeimportance in many technological applications. If such a modificationcan result in a dilatent behavior, additional advantageous applicationscan result. For example, substantial shear thickening can be useful inantimisting applications where a stream of the modified fluid should notbreak into a fine mist, particularly if the stream is produced under ashock situation. Such a shock situation also causes flow with high shearrates which will thicken the fluid and prevent the production of a finemist. The addition of the polymeric material to the jet aviation fuelimproves the antimisting properties of the jet avaiation fuel, such thatupon subjecting the jet aviation fuel to a shock situation the jetaviation fuel will gel. Another example is lubrication under high shearrates, where a higher viscosity produced by the high shear rates canhelp in more effectively separating moving surfaces from coming intocontact.

SUMMARY OF THE INVENTION

The present invention relates to a process for improving the antimistingproperties of a non-polar hydrocarbon liquid, such as jet aviation fuel,which comprises the step of adding a sufficient quantity of a sulfonatedpolymer to the jet aviation fuel.

GENERAL DESCRIPTION OF THE INVENTION

The present invention relates to a process for improving the antimistingproperties of a non-polar hydrocarbon liquid, such as jet aviation fuel,which comprises the step of adding a sufficient quantity of a sulfonatedpolymer to the jet aviation fuel.

FIGS. 1 and 2 schematically display the generalized behavior ofnon-Newtonian fluids. In FIG. 1 it is shown that a fluid can exhibit acombination of Newtonian, dilatant and pseudo-plastic responses atvarious shear rate ranges. Not all the elements shown in FIG. 1 need tobe present for one given fluid. If, for example, point A would beextended to infinite shear rate, the liquid would be purely Newtonian.If the portion A, B, C would be missing such as in A, A', and point A'would be made to coincide with point D, the liquid would be an ordinarypseudo-plastic one. Dilatant fluids can show a shear thickening regionstarting after a Newtonian one such as in A, B or after someshear-thinning as in A, A', B'. A dilatant fluid may exhibitcombinations of Newtonian and pseudoplastic responses at very high shearrates.

The behavior shown in FIG. 1 can be an equilibrated response or a pseudosteady-state response (one achieved in flow where higher shear isexperienced for short times only, such as in short tubes or dies). Ingeneral the fluid can respond with a viscosity or shear stress whichchanges with time under a given shear rate. This is shown in FIG. 2. Ifno time dependent viscosity is observed, the viscous response isequilibrated very quickly (relative to the capability of a measuringdevice to descriminate change under time) and curves A or A' areobserved; this is the usual case for low molecular weight liquids and inmany cases for polymer solutions as well. Some fluids, usuallydispersions or polymer solutions, may exhibit a viscosity change withtime under shear, as shown in FIG. 2. When the viscosity grows withtime, the fluid is rheopectic and when the viscosity diminishes withtime the fluid is thixotropic, as shown by the solid and the brokenlines in FIG. 2 respectively. The time dependence is usually more severeat higher shear rates. Also, this discussion is limited to fluids thatcan reversibly undergo the same behavior after they were allowed torelax under no shear for some time. Liquids that show a permanentviscosity change associated with a permanent structure change with time(such as in a chemical reaction) are of no interest in this invention.

Given a polymer which can exhibit associations between neighboringpolymer chains after it has been dissolved in a solvent, such solutionscan exhibit shear thickening behavior at given concentration ranges.Moreover, given a cosolvent that can alter the association strength (upor down) the solutions can be made to exhibit shear thickening atvarious polymer concentrations or at different shear rate ranges whilethe viscosity levels can also be altered. The "design" criteriondeveloped in this invention is based on the reduced viscosity vs.concentration profiles for a given system.

The necessary element for this invention is an associating polymersolution and the adjustability of the association strength via anadjustment in the polymer structure or the solution nature.

The concentration range in which an associating polymer solution in asolvent, or a solvent modified by the various elements described aboveshows shear thickening behavior is determined by the reduced viscosityof the system.

FIG. 3 shows a general behavior of reduced viscosity (η sp/C) of apolymer solution for an associating and a non-associating polymer of thesame family and molecular weight. The difference between both thesepolymers is either the absence of the associating species in one of thepolymers or the "neutralization" of the associating capability in thispolymer (via an additive, a chemical change or other means). This pointwill be further clarified in the example discussed later. The two curvesshown in FIG. 3, whether their terminal slope (at zero concentration) isnegative, positive or zero will tend to intersect at concentrationC_(A). It is claimed that a shear thickening behavior will be expectedto result for the solution of an associating polymer at a concentrationrange of 0.1 times C_(A) to 10 times C_(A) and most preferably in aconcentration range of 0.3 times C_(A) to 3 times C_(A).

C_(A) in FIG. 3 will strongly depend on all the elements that wereclaimed above as being necessary or desired in the solution system.Weakening the association by using a combination of these elements willmove C_(A) up while strengthening the associations will move C_(A) down.High C_(A) values will tend to reduce the viscosity level of the shearthickening range to higher shear rates. Increasing C_(A) by a lowermolecular additive will tend to reduce viscosity dependence on timeunder shear. Inherently weaker associations, which do not require anadditive if C_(A) needs to be increased, will tend to raise thedependence of viscosity on time under shear.

The crossover of the two curves in FIG. 3 can be hypothesized as aprobable response of all associating polymers where associations can bemostly intramolecular at low concentration and intermolecular at orabove the crossover concentration (C_(A)). Reducing the associationlevel or strength will tend to raise C_(A) and force the associatingcurve to coincide with the nonassociating one when all associations havebeen impaired.

In order for the polymeric solutions of the instant invention to exhibitdilatant behavior the polymer concentration must be such that there ispolymer coil overlap. This concentration is deduced on a theoreticalbasis as being about ##EQU2## wherein C_(A) is the concentration of thepolymer in solution and [η] is the intrinsic viscosity of the solutionwhich is directly related to the molecular weight of the polymer. Onthis basis, the preferred terminology of 0.3 C_(A) to 3 C_(A) is adirect measure of the concentration range of the polymer wherein:##EQU3##

The component materials of the instant process comprise a waterinsoluble, neutralized sulfonated polymer at a critical solutionconcentration level of about 0.1 to 3.0 weight percent dissolved in anonpolar hydrocarbon liquid.

In general, the water insoluble neutralized sulfonated polymer willcomprise from about 5 to about 200 meq. pendant sulfonate groups per 100grams of polymer, more preferably from 10 to 100 meq. pendant sulfonategroups. The sulfonated polymers utilized in the instant invention aregenerally neutralized with the basic materials selected from Groups IA,IIA, IB and IIB of the Periodic Table of Elements and lead, tin andantimony, as well as ammonium and amine counterions. Elements which areknown as transition elements, such as nickel and cobalt, are also usefulin neutralizing the sulfonated polymers of the instant invention.Sulfonated polymers which are subject to the process of the instantinvention are illimitable and include both plastic and elastomericpolymers. Specific polymers include sulfonated polystyrene, sulfonatedt-butyl styrene, sulfonated ethylene copolymers, sulfonated propylenecopolymers, sulfonated styrene/acrylonitrile copolymers, sulfonatedstyrene/methyl methacrylate copolymers, sulfonated block copolymers ofstyrene/ethylene oxide, acrylic acid copolymers with styrene, sulfonatedpolyisobutylene, sulfonated ethylene-propylene terpolymers, sulfonatedpolyisoprene, and sulfonated elastomers and their copolymers. Thepreferred polymers of the instant invention are ethylene-propyleneterpolymers and polystyrene.

Neutralization of the cited polymers with appropriate metal hydroxides,metal acetates, metal oxides, or ammonium hydroxide etc., can beconducted by means well-known in the art. For example, the sulfonationprocess as with Butyl rubber, containing a small 0.3 to 1.0 mole percentunsaturation, can be conducted in a suitable solvent such as toluene,with acetyle sulfate as the sulfonating agent, such as described in U.S.Pat. No. 3,836,511. The resulting sulfonic acid derivative can then beneutralized with a number of different neutralization agents such as asodium phenolate and similar metal salts. The amounts of suchneutralization agents employed will normally be equal stoichiometricallyto the amount of free acid in the polymer plus any unreacted reagentwhich is still present. It is preferred that the amount of neutralizingagent be equal to the molar amount of sulfonating agent originallyemployed plus 10 percent more to ensure full neutralization. The use ofmore of such neutralization agent is not critical. Sufficientneutralization agent is necessary to effect at least 50 percentneutralization of the sulfonic acid groups present in the polymer,preferably at least 90 percent, and most preferably essentially completeneutralization of such acid groups should be effected. Thus, the degreeof neutralization of said sulfonate groups may vary from 0 (free acidform) to 100 mole percent, preferably 90 to 100 percent, and mostpreferably about 99 to about 100 percent. With the utilization ofneutralized sulfonated polymers in this instant invention, particularlysulfonated EPDM polymers it is preferred that the degree ofneutralization be substantially complete, that is with no substantialfree acid present and without substantial excess of the base other thanthat needed to ensure neutralization. The neutralized sulfonatedpolymers possess greater thermal stability compared to its acid form.Thus, it is clear that the polymers which are normally utilized in theinstant invention comprise substantially neutralized pendant groups, andin fact, an excess of the neutralizing material may be utilized withoutdefeating the objects of the instant invention.

The neutralized sulfonated polymers of the instant invention may vary innumber average molecular weight from 1,000 to 10,000,000, preferablyfrom 5,000 to 500,000, most preferably from 10,000 to 200,000. Thesepolymers may be prepared by methods known in the art, for example, seeU.S. Pat. No. 3,642,728, hereby incorporated by reference.

The preferred neutralized sulfonated polymers for use in the instantinvention, e.g., sulfonated EPDM terpolymers and substituted derivativesthereof, may be by the procedures described in U.S. Pat. No. 3,870,841,filed Oct. 2, 1972, in the names of H. S. Makowski, R. D. Lundberg andG. H. Singhal, hereby incorporated by reference.

The water insoluble, neutralized sulfonated polymers may be incorporatedinto the hydrocarbon liquid at a level of from 0.1 to 3.0 weight percentand more preferably from 0.1 to 2.00 weight percent, based on thepolymer molecular weight and, if present, the amount of polar cosolvent.

Specific examples of preferred sulfonated polymers which are useful inthe instant invention include sulfonated polystyrene, sulfonatedpoly-t-butyl styrene, sulfonated polyethylene (substantiallynoncrystalline), and sulfonated ethylene copolymers, sulfonatedpolypropylene (substantially noncrystalline), and sulfonatedpolypropylene copolymers, (styrene)-acrylic acid copolymers, sulfonatedpolyisobutylene, sulfonated ethylene-propylene terpolymers, sulfonatedpolyisoprene, sulfonated polyvinyl toluene, sulfonated polyvinyl toluenecopolymers and isoprenestyrene sulfonate copolymers formed by a freeradical copolymerization process.

The neutralized sulfonated polymers of the instant invention may beprepared prior to incorporation into the organic solvent, or byneutralization of the acid form in situ. For example, preferably theacid derivative is neutralized immediately after preparation. Forexample, if the sulfonation of polystyrene is conducted in solution,then the neutralization of that acid derivative can be conductedimmediately following the sulfonation procedure.

The neutralized sulfonated polymer may then be isolated by meanswell-known to those skilled in the art, i.e., coagulation, steamstripping, or solvent evaporation, because the neutralized polymer hassufficient thermal stability to be dried for employment at a later timein the process of the instant invention. It is well-known that theunneutralized sulfonic acid derivatives do not possess good thermalstability and the above operations avoid that problem.

It is also possible to neutralize the acid form of these sulfonatedpolymers in situ; however, this is not a preferred operation, since insitu neutralization requires preparation of the sulfonic acid in theorganic liquid which is to be subjected to the instant process, or theacid form of the sulfonated polymer must be dissolved in said organicliquid. The latter approach may involve handling of an acid form of ansulfonated polymer which has limited thermal stability. Therefore, it isquite apparent that the preparation and isolation of a neutralizedsulfonated polymer affords the maximum latitude in formulation, lessproblems in handling polymers of limited thermal stability and maximumcontrol over the final solution of the neutralized sulfonated polymer,and organic liquid.

The non-polar organic liquids which have a solubility parameter of lessthan 9.0, which may be utilized in the instant invention, are selectedwith relation to the sulfonated polymer and vice-versa. The hydrocarbonliquid is selected from the group consisting of aromatic and aliphatichydrocarbons,gasoline and jet aviation fuel and mixtures thereof.

Specific examples of hydrocarbon liquids to be employed with the varioustypes of polymers are:

    ______________________________________                                        Polymer           Hydrocarbon Liquid                                          ______________________________________                                        sulfonated polystyrene                                                                          benzene, toluene, ethyl                                                       benzene, xylene, styrene,                                                     ethylene dichloride,                                                          methylene chloride, jet                                                       aviation fuel.                                              sulfonated poly-t-butyl-                                                                        benezene, toluene,                                          styrene           xylene, ethyl benezene,                                                       styrene, t-butyl                                                              styrene, aliphatic                                                            oils, aromatic oils,                                                          hexane, heptane,                                                              decane, nonane, and                                                           light and heavy fuels                                                         jet aviation fuels.                                         sulfonated ethylene-                                                                            Jet aviation fuel, pentane,                                 propylene terpolymer                                                                            aliphatic and                                                                 aromatic solvents, oils                                                       such as Solvent "100                                                          Neutral", "150 Neutral"                                                       and similar paraf-                                                            finic oils,                                                                   benzene, diesel oil,                                                          light fuels, toluene,                                                         xylene, ethyl benzene,                                                        pentane, hexane,                                                              heptane, octane,                                                              isooctane, nonane,                                                            decane aromatic                                                               solvents.                                                   sulfonated polyisobutylene                                                                      saturated aliphatic                                                           hydrocarbons,                                                                 diisobutylene,                                                                triisobutylene,                                                               aromatic and alkyl                                                            substituted aromatic                                                          hydrocarbons,                                                                 aliphatic oils,                                                               oils predominantly                                                            paraffinic in nature                                                          and mixtures containing                                                       naphthenic hydrocar-                                                          bons. "Solvent 100                                                            Neutral", "Solvent 150                                                        Nuetral" and all related                                                      oils, low molecular                                                           weight polymeric oils                                                         such as squalene, white                                                       oils and process oils                                                         having 60 percent or                                                          less aromatic content, jet                                                    aviation fuel.                                              sulfonated polyvinyl                                                                            toluene, benzene, xylene,                                   toluene           cyclohexane, ethyl                                                            benzene, styrene,                                                             jet aviation fuel.                                          ______________________________________                                    

The process of improving the antimisting properties of a jet aviationfuel comprises dissolving about 0.1 to about 1.0 weight percent of theneutralized sulfonated polymer in the jet aviation fuel. The solution ofthe jet aviation fuel and the neutralized sulfonated polymer, whensubjected to shock or a high shear condition, will gel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a plot of viscosity versus shear rate of anon-newtonian fluid;

FIG. 2 illustrates a plot of viscosity versus time under shear forrheopectic or thixotropic fluids; and

FIG. 3 illustrates a plot of reduced viscosity versus solutionconcentration for associating and non-associating polymers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following examples will demonstrate the performance of sulfonatedEPDM terpolymers of varying sulfonate levels in several specific organicliquid solution environments.

Example I

One hundred grams of an EPDM terpolymer, Vistalon 2504-20 (a broken-downversion of Exxon Chemical Vistalon 2504, having a Mooney viscosity of 20or about half of the commercial polymer) was dissolved under agitationin 1000 ml. of n-hexane at 40° C. The resultant cement was cooled toroom temperature and 5.74 ml. of acetic anhydride (60.75 mmoles) wasthen added. While stirring the mixture, 2.1 ml. of 95% H₂ SO₄ (37.5mmoles) was added dropwise. The sulfonation reaction was quenched after30 minutes with 150 ml. of isopropanol. The acid form of the sulfonatedpolymer was analyzed by Dietert Sulfur Analysis to have 33 meq. of S03Hgroups per 100 grams of sulfonated polymer. To the quenched sulfonatedcement was added with stirring for thirty minutes 25.6 grams (90mmoles/100 grams of EPDM) of stearic acid. A solution of 9.87 grams (90meq./100 g. of EPDM) of zinc acetate dihydrate dissolved in 25 ml. ofdistilled water was then added in the cement and the cement stirred foran additional 30 minutes. Antioxidant 2246 (0.5 grams) was then added tothe cement. The resultant plasticized, neutralized sulfonated EPDMterpolymer was then isolated by steam stripping and drying on a rubbermill at 220° F., wherein the sulfonated terpolymer has an apparentviscosity at 0.73 sec⁻¹ at 200° C. of about 3.3×10⁵ poise.

EXAMPLE II

A solution of a sulfonated EPDM in xylene was prepared at aconcentration of 1.75 weight percent by using a magnetic stirrer.

The sulfonated EPDM was a zinc salt with a sulfonation level of 10meq./100g (TP-398). The viscosity-shear rate response was studied with arotational viscometer (Haake CV-100) at 25° . It was found that thesolution exhibited a dilatant response as shown in Table I.

                  TABLE I                                                         ______________________________________                                        Viscosity vs. Shear Rate for a Zinc--Sulfo EPDM                               Solution in Xylene at 1.75 Wt. % and 25° C.                                   Shear Rate                                                                            Viscosity                                                             sec.sup.-1                                                                            cP                                                             ______________________________________                                                3       13                                                                   10      152                                                                   20      190                                                                   30      290                                                                   60      590                                                            ______________________________________                                    

EXAMPLE III

A solution of the sulfonated EPDM described in Example II was preparedin xylene at a concentration of 2.5 weight percent.

The viscosity-shear rate behavior was measured as described in ExampleII and the results are as shown in Table II.

                  TABLE II                                                        ______________________________________                                        Viscosity vs. Shear Rate for a Zinc--Sulfo EPDM                               Solution in Xylene at 2.5 Wt. % and 25° C.                                    Shear Rate                                                                            Viscosity                                                             sec.sup.-1                                                                            cP                                                             ______________________________________                                               3       12,300                                                                5       15,600                                                                7.5     19,800                                                         ______________________________________                                    

Examples II and III demonstrate a dilatant behavior of sulfo EPDMsolutions in an organic solvent containing no cosolvent.

What is claimed is:
 1. A method for improving the antimisting propertiesof an organic liquid which comprises the step of dissolving about 0.1 toabout 3.0 weight percent of a neutralized sulfonated polymer in suchorganic liquid, having a solubility parameter of less than 9, whereinsaid neutralized sulfonated polymer has about 5 to about 200 meq. ofpendant sulfonate groups per 100 grams of polymer and about 90.0 to 100%of said sulfonate groups are neutralized, wherein the solution of theorganic liquid and the neutralized sulfonated polymer has an approximatepolymer concentration, C_(A), which can be characterized by the formula:##EQU4## wherein [η] is the intrinsic viscosity of said solution and thepolymer concentration range is 0.1 times C_(A) to 10 times C_(A).
 2. Amethod according to claim 1 wherein said sulfonate groups areneutralized within an ammonium or metal counterion.
 3. A methodaccording to claim 2 wherein said metal counterion is selected from thegroup consisting of antimony, tin, lead and Groups IA, IIA, VIA, VIIA,VIIIA, IB and IIB of the Periodic Table of Elements.
 4. A methodaccording to claim 1 wherein said neutralized sulfonated polymer isformed from an elastomeric polymer.
 5. A method according to claim 4wherein said elastomeric polymer is selected from the group consistingof EPDM terpolymer and Butyl rubber.
 6. A method according to claim 1wherein said neutralized sulfonated polymer is formed from athermoplastic.
 7. A method according to claim 6 wherein saidthermoplastic is selected from the group consisting of polystyrene,t-butyl styrene, ethylene copolymers, propylene copolymers andstyrene/acrylonitrile copolymers.
 8. A method according to claim 1wherein said organic liquid is selected from a group consisting ofaliphatic hydrocarbons and aromatic hydrocarbons.
 9. A method accordingto claim 1 wherein said organic liquid is selected from the groupconsisting of benzene, toluene, ethyl benzene, xylene and styrene andmixtures thereof.
 10. A method according to claim 1 wherein saidneutralized sulfonated polymer is formed from polystyrene.
 11. A methodaccording to claim 1 wherein said hydrocarbon liquid is gasoline or ajet aviation fuel.